dysthymia

DEFINITION (DSM-5 Persistent Depressive Disorder, PDD): Depressed mood for most of the day, more days than not, for ≥2 years in adults (≥1 year in children/adolescents, where mood may be irritable). Requires ≥2 of the following while depressed: poor appetite or overeating; insomnia or hypersomnia; low energy/fatigue; low self-esteem; poor concentration or difficulty making decisions; hopelessness. (Mnemonic: "HE SLEEPS CD" - Hopelessness, Energy low, Sleep changes, Low self-esteem, Eating changes, Poor concentration, Sleep, Concentration, Decisions.) The person has never been without symptoms for more than 2 months at a time. Symptoms cause clinically significant distress or impairment. Criteria for mania/hypomania or cyclothymia have never been met, and symptoms are not due to a substance or medical condition.

KEY EXAM POINTS: - Dysthymia = chronic and milder; Major Depressive Disorder (MDD) = episodic and more severe (≥5 symptoms for ≥2 weeks, including depressed mood or anhedonia). - "Double depression": a major depressive episode superimposed on underlying dysthymia. Patients are less likely to fully recover between episodes, and this carries a worse prognosis. - Patients often describe themselves as having "always been sad" or "gloomy"; onset is often early (childhood, adolescence, or early adulthood). - No psychotic features in the definition (psychosis would suggest a different diagnosis or a superimposed major depressive episode with psychotic features). - Rule out: hypothyroidism, substance use, medical illness, bipolar disorder, and other causes of chronic fatigue.

EPIDEMIOLOGY AND RISK FACTORS: Lifetime prevalence is about 3-6%. It is more common in women. Risk factors include family history of depression, early-life adversity, chronic stress, and comorbid anxiety, substance use, or personality disorders. Higher comorbidity with MDD, anxiety disorders, and substance use disorders.

PATHOPHYSIOLOGY: Likely similar to MDD, with decreased monoamine (serotonin, norepinephrine, dopamine) neurotransmission, HPA axis dysregulation, and genetic and environmental contributors.

MANAGEMENT: - First-line: SSRIs (e.g., sertraline, escitalopram) and/or psychotherapy (CBT; also interpersonal therapy and CBASP, cognitive behavioral analysis system of psychotherapy, which was developed for chronic depression). Combination therapy is often most effective. - Alternatives: SNRIs, bupropion, and others; response may be slower than in MDD, so allow an adequate trial (often 8-12 weeks). - Treatment is often long term because of the chronic course and high relapse risk.

COMPLICATIONS: Increased risk of developing major depressive episodes, suicide, impaired social and occupational functioning, and substance use.

DIFFERENTIAL: MDD (episodic, more severe), bipolar disorder/cyclothymia (hypomanic symptoms present), adjustment disorder with depressed mood (identifiable stressor, within 3 months of onset, resolves within 6 months after the stressor ends), depression due to a medical condition (e.g., hypothyroidism), and substance-induced depressive disorder.